netdev - Re: [PATCH net 3/4] net: hns3: fixed vf get max channels bug

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Message-ID: <20250708163512.GT452973@horms.kernel.org>
Date: Tue, 8 Jul 2025 17:35:12 +0100
From: Simon Horman <horms@...nel.org>
To: Jijie Shao <shaojijie@...wei.com>
Cc: David Laight <david.laight.linux@...il.com>, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	andrew+netdev@...n.ch, shenjian15@...wei.com,
	liuyonglong@...wei.com, chenhao418@...wei.com,
	jonathan.cameron@...wei.com, shameerali.kolothum.thodi@...wei.com,
	salil.mehta@...wei.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 3/4] net: hns3: fixed vf get max channels bug

On Tue, Jul 08, 2025 at 05:37:11PM +0800, Jijie Shao wrote:
> 
> on 2025/7/5 15:24, David Laight wrote:
> > On Fri, 4 Jul 2025 17:05:37 +0100
> > Simon Horman <horms@...nel.org> wrote:
> > 
> > > + David Laight
> > > 
> > > On Wed, Jul 02, 2025 at 09:09:00PM +0800, Jijie Shao wrote:
> > > > From: Hao Lan <lanhao@...wei.com>
> > > > 
> > > > Currently, the queried maximum of vf channels is the maximum of channels
> > > > supported by each TC. However, the actual maximum of channels is
> > > > the maximum of channels supported by the device.
> > > > 
> > > > Fixes: 849e46077689 ("net: hns3: add ethtool_ops.get_channels support for VF")
> > > > Signed-off-by: Jian Shen <shenjian15@...wei.com>
> > > > Signed-off-by: Hao Lan <lanhao@...wei.com>
> > > > Signed-off-by: Jijie Shao <shaojijie@...wei.com>
> > > Reviewed-by: Simon Horman <horms@...nel.org>
> > > 
> > > > ---
> > > >   drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c | 6 +-----
> > > >   1 file changed, 1 insertion(+), 5 deletions(-)
> > > > 
> > > > diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c b/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > > > index 33136a1e02cf..626f5419fd7d 100644
> > > > --- a/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > > > +++ b/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > > > @@ -3094,11 +3094,7 @@ static void hclgevf_uninit_ae_dev(struct hnae3_ae_dev *ae_dev)
> > > >   static u32 hclgevf_get_max_channels(struct hclgevf_dev *hdev)
> > > >   {
> > > > -	struct hnae3_handle *nic = &hdev->nic;
> > > > -	struct hnae3_knic_private_info *kinfo = &nic->kinfo;
> > > > -
> > > > -	return min_t(u32, hdev->rss_size_max,
> > > > -		     hdev->num_tqps / kinfo->tc_info.num_tc);
> > > > +	return min_t(u32, hdev->rss_size_max, hdev->num_tqps);
> > > min_t() wasn't needed before and it certainly doesn't seem to be needed
> > > now, as both .rss_size_max, and .num_tqps are u16.
> > It (well something) would have been needed before the min_t() changes.
> > The u16 values get promoted to 'signed int' prior to the division.
> > 
> > > As a follow-up, once this change hits net-next, please update to use min()
> > > instead. Likely elsewhere too.
> > Especially any min_t(u16, ...) or u8 ones.
> > They are just so wrong and have caused bugs.
> > 
> > 	David
> 
> 
> Does this mean that min_t() will be deprecated?
> If so, I will replace all instances of min_t() with min() in the hns3 driver.

No, it means that min_t() should only be used when it is needed.
AFAIK, basically when the operands need to be cast.